As a kind of typical group III and group V element compound films, gallium nitride (GaN) is a material widely used to manufacture a blue light emitting diode, a purple light emitting diode, a white light emitting diode, an ultraviolet detector and a high power microwave transistor. Since GaN has practical and potential applications in manufacturing low energy consumption devices (such as an LED) which are widely used, GaN film growth has attracted great attention.
The GaN film may grow with various methods, including a molecular beam epitaxy (MBE) method, a hydride vapor phase epitaxy (HVPE) method, a metal organic chemical vapor deposition (MOCVD) method and so on. At present, the MOCVD method is a preferred deposition method for obtaining a film with enough quality used for the manufacture of an LED.
The MOCVD process is generally performed in a reactor or a reaction chamber at a relatively high temperature by a thermal processing method. Generally, a first precursor gas including a group III element (such as gallium (Ga)) and a second precursor gas (such as ammonia (NH3)) including nitrogen are fed into the reaction chamber by a gas transportation apparatus to react so as to form a GaN film on a heated substrate. A carrier gas may also be used to assist the transportation of the precursor gases onto the substrate. A group III nitride film (such as a GaN film) is formed by the mixed reaction of the precursor gases on a heated surface of the substrate and then is deposited on the surface of the substrate.
However, during the MOCVD film growth process, the GaN film or other reaction products are not only grown or deposited on the substrate, but also grown or deposited on the inner surface of the reaction chamber including the surface of the gas transportation apparatus. These undesired deposits or residues are accumulated, which may produce adhered aggregates such as powder and particles in the reaction chamber, and may peel off from the adhering surface to spread everywhere in the reaction chamber along with the flow of the reaction gases and to finally fall on the processed substrate, thereby causing defects or ineffective of the substrate and contamination in the reaction chamber which has adverse effects on the quality of the next MOCVD process. Thus, after the MOCVD film growth process is performed for a period of time, the film growth process has to be stopped to specially carry out a cleaning process for the reaction chamber, i.e. to remove the aggregates adhered to the gas transportation apparatus.
At present, the method for cleaning the gas transportation apparatus in the art is “manual cleaning”. That is, an operator must stop the film growth process, open a top cover of the reaction chamber after the temperature in the reaction chamber is reduced to a certain temperature, manually brush away the deposits or residues adhered to the gas transportation apparatus from the adhering surface with a brush, and remove them to the outside of the reaction chamber by a vacuum suction method. If the deposits or residues are very thick, the operator needs to manually scrape off them from the adhering surface with a tool and remove them to the outside of the reaction chamber. This cleaning method has some disadvantages. Specifically, for performing the cleaning process, the film growth process needs to be stopped, and it has to wait for a quite long time allowing the temperature in the reaction chamber to be reduced to a suitable temperature for the manual cleaning, and it has to be manually performed by the operator under the condition that the top cover of the reaction chamber is opened. Thus, for a user of the reaction chamber, the throughput of the process production of the reaction chamber is reduced, and the use cost of the producer is increased. Further, due to the “manual cleaning”, it is impossible to realize automatic cleaning process of the system, and to ensure the consistent results of cleaning process, causing that deviations and defects in process quality may occur in the subsequent film growth process.
Therefore, there is a need to develop an apparatus and method for cleaning the gas transportation apparatus and the inner surface of the reaction chamber, which is highly automatic, effective and timesaving, and may ensure the quality and consistency of cleaning, and does not have adverse effects on the subsequent film growth.